The invention relates to a disc brake having a brake caliper, which straddles a brake disc and in which brake pads are arranged having friction linings. The brake pads can be pressed, in each case, on both sides against friction rings of the brake disc.
In connection with attempts, for reasons of environmental protection, to reduce fine dust loading of the air, there are also demands for the prevention of brake dust emissions.
Owing, in particular, to the small particle size and the content of metallic constituents, the abraded material that is formed during braking from the friction lining and the brake disc is increasingly being viewed critically.
Various attempted solutions are known in this regard in the prior art, these being divided essentially into brake-dust collecting and brake-dust filtering devices. However, the known designs do not meet the requirements set to a satisfactory extent.
Brake-dust collectors, which are usually designed as gravity separators, are not suitable for avoiding fine dust emissions since only relatively coarse particles are caught and removed by gravity. At particle sizes <10 μm, gravity separation is no longer possible.
Brake-dust filtering devices, on the other hand, can retain even very fine dust particles, given an appropriate choice of filter material.
WO 2008/083884 A1 discloses the use of a brake-dust filtering device of this kind which has a fine-dust filter on one side of the brake disc of a disc brake and a fan on the other side, both being positioned in a wheel rim. The fine-dust filter is held on the rim in a manner hermetically sealed-off from the environment.
To ensure a through flow of the abraded material which arises during braking, air is sucked in through the rim by the fan and, taking the abraded material along with it, is passed through the fine-dust filter, where dust particles are filtered out.
Since the brake disc is to this extent closed off by the fine-dust filter on one side and by the fan on the other, the necessary cooling of the composite lining disc brake is achieved exclusively by means of the air introduced by the fan.
The flow rates necessary for adequate heat dissipation require that the filtering device should be of significant dimensions, but the available quantities of cooling air are, in many cases, still insufficient. This is associated with increased braking temperatures and with an increase in brake wear resulting therefrom. Particularly as regards operating costs, the known device is therefore not conducive to optimized use.
A similar view must also be taken of the fact that dirt is also sucked in from the environment with the cooling air, with the result that the fine-dust filter has only a relatively short service life. A fine-dust filter of this kind must therefore be replaced at very short intervals.
It is the underlying object of the invention to develop a disc brake such that the material abraded during braking is prevented from escaping into the environment, while operating costs are minimized.
This and other objects are achieved by a disc brake having a brake caliper, which straddles a brake disc and in which brake pads are arranged having friction linings. The brake pads can be pressed, in each case, on both sides against friction rings of the brake disc. The friction rings are covered by a housing outside the region where the friction rings overlap with the friction linings. The housing is stationary with respect to the brake caliper and is connected to a suction device, wherein a dust removal device is provided between the housing and the suction device.
By means of this design embodiment, virtual encapsulation of the friction rings of the brake disc is achieved, covering both the useful surface, i.e. the friction surface, and the peripheral surface defined by the thickness of the friction rings.
In this arrangement, the peripheral covering surface forms a circular collar, with a similar collar also being provided on the inner circumference, and the housing according to the invention thus forms a hood which is open only in the region of overlap of the friction lining of the brake pad.
The covering surfaces of the housing, which is stationary with respect to the brake caliper and is attached thereto or to a fixed-location brake carrier, is positioned with a slight clearance relative to the covered regions.
At the inner and outer circumference, the housing is designed as a gap seal, e.g. as a labyrinth seal, which allows fresh air to be sucked in during the operation of the suction device, taking along the abraded material that arises during braking.
The covering parts that cover the friction rings present on both sides of the brake disc can be connected to one another by connecting tabs, wherein the connecting tabs are arranged spaced apart, giving rise to sufficiently large free zones, through which unhindered cooling by air exchange remains assured in the case of an internally ventilated brake disc.
It is expedient if each housing consists of two parts in the form of semicircular segments, which are connected to one another by screw connection, for example, allowing very easy assembly and disassembly.
A suction line, which is connected to the suction device, opens into the gap volume formed between the housing and the associated friction ring, wherein a common suction line is provided for both housings.
The dust removal device arranged between the suction device and the housing preferably consists of a coarse-dust separator, which is arranged upstream in the direction of the housing, and a fine-dust filter. The contaminated extracted air is guided through the coarse-dust separator toward the fine-dust filter, which is connected ahead of the suction device, preferably a suction fan. A muffler is provided downstream of the suction fan, through which muffler the air which has been cleaned to this extent is released into the atmosphere.
It is expedient if the suction device is switched by way of a switching unit, which is coupled to the braking device and is controlled in such a way that the suction device remains in operation for a certain time, even after braking has ended. In free, unbraked travel and after the predetermined after-running time, extraction is unnecessary. It is thus possible, with relatively small extraction air rates, to achieve effective filtering that is distinguished especially by low operating costs.
Another contributing factor to this is the fact that the arrangement of the coarse-dust separator ahead of the fine-dust filter means that the latter is subjected to significantly lower loading than was previously the case, in particular because the gap seals mentioned between the friction rings or the brake linings and the housing ensure that no extraneous dirt but only ambient air, i.e. fresh air as it were, is sucked in.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.